The present invention is directed to packaging components (e.g., a lid, a container, etc.) for packaging microelectronic devices (for example, semiconductor devices), packages (assemblies) formed using these packaging components (e.g., to form integrated microelectronic assemblies), and methods of forming the packaging components and packages. The present invention is especially directed to packaging components and packages formed utilizing such components, and methods for forming such components and such packages, which avoid damage and degradation of the microelectronic devices in such packages, due to hydrogen in the package. Thus, the present invention is directed to packaging components and packages, having hydrogen gettering structure, which avoid hydrogen degradation of packaged devices, particularly those devices having a low threshold hydrogen level in the hermetic (air-tightly sealed) package.
A problem experienced by semiconductor manufacturers, in connection with packaged semiconductor devices, is hydrogen degradation of the devices in hermetically sealed package. The hydrogen within the package can be generated from various parts of the package (for example, from housing materials, plated nickel layers, Eccosorb (a material used in semiconductor packages of, e.g., millimeter wave integrated circuits, to absorb electrical signals), epoxy adhesives, etc.).
This problem of hydrogen degradation is particularly acute with devices such as pseudomorphic high electron mobility transistors (PHEMTs) of monolithic millimeter wave integrated circuits (MMICs). Because these devices have thin nitride passivation layers, they are especially sensitive to hydrogen degradation, and a threshold hydrogen level in hermetic packages of these types of devices is very low, for example, about 100 ppm. However, such PHEMTs of MMICs are not the only types of devices particularly sensitive to hydrogen degradation; for example, MESFETs and indium phosphide high electron mobility transistors are other types of devices that are especially sensitive to hydrogen degradation and have very low threshold hydrogen levels in the hermetically-sealed package.
It has been proposed to mitigate the problem of hydrogen degradation, by baking out housing materials prior to populating the microelectronic device in the package and then sealing. While this has been successful in some instances, such technique to mitigate the problem of hydrogen degradation has not been sufficient, particularly with devices having a low hydrogen threshold level.
Another technique to overcome this problem of hydrogen degradation involves suspending inorganic hydrogen-absorbing material in silicone, in the device package. The inorganic hydrogen absorption material can be any of known metal oxide hydrogen getters. However, this technique has problems when utilized in packaging, e.g., microelectronic devices. For example, the material used undesirably takes up a large amount of moisture, requiring careful handling during the package sealing process. In addition, silicone may vaporize and contaminate electronic device and laser seal surfaces, and additional problems arise with the packaged device due to mobile impurity ions (for example, K+, Na+, Clxe2x88x92, etc.) introduced due to this inorganic hydrogen absorption material in silicone in the package.
Accordingly, it is an objective of the present invention to provide a packaging component (e.g., a lid, a container, etc.) having hydrogen gettering structure which is stable, does not require activation (as a getter) at high temperatures, and which does not absorb moisture, corrode or actively react with oxygen or moisture.
It is a further objective of this invention to provide a package (i.e., packaged microelectronic device) using this packaging component, and a method of making this packaging component and this package.
It is a further objective of the present invention to provide a packaging component, having hydrogen gettering structure which strongly adheres to a surface of the packaging component, a package formed utilizing such component, and methods of making this component and package.
It is a still further objective of the present invention to provide a packaging component, having hydrogen gettering structure which does not release hydrogen when a package having this component is heated at temperatures below 150xc2x0 C., and a package using such component and methods of making such component and such package.
The foregoing objects are achieved by the packaging component of the present invention, which includes a housing member and sequentially deposited metal layers attached to the housing member, the sequentially deposited metal layers being positioned within the package when the components of the package are assembled to form the package, this sequentially deposited metal layers including an absorbing layer of a metal for absorbing hydrogen, and an outermost layer (that is, a layer in contact with the environment within the package when the package has been assembled) of a metal that converts hydrogen molecules to hydrogen atoms and also absorbs hydrogen, adjacent to the absorbing layer of metal for absorbing hydrogen, the metal of the outermost layer being of a different metal than the metal of the absorbing layer. Illustratively, and not to be limiting, the metal of the outermost layer is palladium; and the absorbent layer can be made of zirconium or titanium.
Furthermore, in order to improve adherence of the sequentially deposited layers of metal layers to the housing member, as well as to further absorb hydrogen, the sequentially deposited layers of metal layers further includes, in addition to the aforementioned two layers, a first layer of a first metal, different than the metal of the aforementioned two layers, closer to the housing member than are the other two layers, for adhering to the housing member and for trapping hydrogen. This first layer of a first metal (e.g., nickel) has greater adherence to the housing member than the metal (e.g., zirconium or titanium) of the absorbing layer.
This two-layer (or three-layer) sequentially deposited layers of metal layers, the layers respectively being made of different metals, functions as hydrogen gettering structure in the assembled package containing a microelectronic device (e.g., a semiconductor device).
In some instances, the two-(or three-) layer sequentially deposited layers may provide sufficient hydrogen gettering in the package; however, for acutely sensitive devices, where the hydrogen threshold level is very low (for example, power pseudomorphic high electron mobility transistors of monolithic millimeter wave integrated circuits, or MESFETs, or indium phosphide high electron mobility transistors), the sequentially deposited layers of metal layers preferably further includes at least one further absorbing layer of, e.g., the hydrogen-absorbing metal, e.g., selected from the group consisting of zirconium or titanium, and at least one further first layer, of, e.g., nickel, positioned between the layer (e.g., of nickel) closest to the housing member surface and the layer (e.g., of zirconium or titanium) adjacent the outermost layer.
The present invention also achieves the foregoing objectives through a packaged microelectronic device, including a plurality of components forming a sealed package, these plurality of components including a container for holding the microelectronic device and a lid, the plurality of components including a component containing the aforementioned sequentially deposited layers of metal layers, with the microelectronic device being adhered to a bottom of the container, the lid being sealed to the container by an air-tight seal.
The foregoing objectives are also achieved by a method of fabricating a package component, of a package for packaging a microelectronic device, having the steps of:
(a) providing a housing member of the package;
(b) depositing a first metal, of a metal for absorbing hydrogen, overlaying a surface of the housing member which will be an inside surface of the package; and
(c) depositing a second metal layer, which is an outermost layer of metal layers overlaying the surface of the housing member, of a metal that converts hydrogen molecules into hydrogen atoms and absorbs hydrogen, this second metal layer being deposited adjacent the first metal layer and being of a different metal than the metal of the first metal layer.
Illustratively, and not to be limiting, this first metal layer is made of a metal selected from the group consisting titanium or zirconium, and the second metal layer is made of palladium. The first and second metal layers can, illustratively, be deposited by a process of electronbeam evaporation deposition or a process of sputtering.
In order to further achieve the benefits of the present invention, prior to depositing the aforementioned first metal layer, a third metal layer, of a different metal than that of the first and second metal layers, which absorbs hydrogen and has a greater adherence to the housing member (or to a layer adhered to the housing member) than does metal of the first metal layer, is deposited over (e.g., on the housing member, the first metal layer being deposited on the third metal layer.
Desirably, prior to depositing the metal layers, the surface of the housing member upon which the metal layers are to be deposited is roughened, which improves hydrogen absorption efficiency of the sequentially deposited layers of metal layers.
The foregoing objectives are further achieved by a method of packaging a microelectronic device, thereby forming an integrated microelectronic assembly, which includes steps of:
(a) providing packaging components, for packaging the microelectronic device in an air-tight sealed package, including a lid and a container for holding this microelectronic device, the packaging components including a package component with the sequentially deposited layers of metal layers as discussed previously;
(b) providing the microelectronic device;
(c) inserting the microelectronic device in the container; and
(d) air-tightly sealing the lid on the container.
Accordingly, through the present invention a package having a hydrogen gettering structure which is stable and has a high pumping speed, does not require activation at high temperature or a vacuum bake, does not absorb moisture, and does not corrode or actively react to oxygen or moisture, is achieved. The metal layers of the sequentially deposited layers can easily and simply be deposited on package components prior to package assembly. The sequentially deposited layers have physical strength and good adherence to the housing member, and provides multiple hydrogen reservoirs for the gettering function. Moreover, with the combination of layers utilized, any formation of powdery hydride can be blocked from contaminating electronic circuits in the package.